1. Field of the Invention
The present invention relates to a cavity resonator coupling-type power distributor/power combiner. More particularly, it relates to a distributor/combiner of a cavity resonator coupling-type for distributing or combining microwave electric power between a single coupling terminal and a plurality of coupling terminals.
2. Description of the Prior Art
In recent years, attempts have been made to use semiconductor amplifier elements, such as gallium-arsenide (GaAs) field effect transistors (FET's) instead of conventional traveling-wave tubes to amplify signals in the microwave band. The semi-conductor amplifier element, however, has an output power of several watts at the greatest, and when it is necessary to amplify a high frequency signal with a large electric power, such elements must be operated in parallel. Because of this, a conventionally accepted practice is to distribute input signals in the microwave band into a plurality of channels by a microwave distributor, to amplify the signals of each channel by one of the above-mentioned semiconductor amplifier elements, and to combine the amplified output signals of each of the channels into a signal of one channel by a microwave combiner, thereby obtaining a high frequency signal with large electric power. The electric power, however, is lost when the phases and the amplitudes of the microwave electric power distributed by the microwave distributor are not in agreement, or when the microwave electric power is not combined in phase and in equal amplitude by the microwave combiner. It is, therefore, desired that the phases and the amplitudes of microwave signals should be uniformly distributed in the microwave distributor and in the microwave combiner. It is also necessary that the distributor and the combiner lose as little electric power as possible.
Hybrid junction circuits are conventionally used for distributing or combining microwave electric power. The hybrid junction circuits, however, have disadvantages in that considerable insertion loss occurs therein and they require a relatively large area due to the microstrip lines constituting the hybrid junction circuits.
A cavity resonator may be effectively used as a distributor or a combiner because it can provide a high coincidence of both phase and electric power between the input and the output thereof. Conventionally, only a single cavity resonator is present. A single cavity resonator, however, has a very narrow bandwidth which limits its use as a distributor or a combiner. Therefore, a single cavity resonator cannot be practically used as a distributor or a combiner.